The invention pertains to a rotatable cutting tool that has a hard insert at the axial forward end thereof, the hard insert itself, and an assembly that includes the rotatable cutting tool and a tool holder.
Heretofore, for applications such as road planning rotatable cutting tools have been used to break up the earth strata (e.g., asphalt pavement, asphaltic concrete or the like). Typically, the cutting tool has a hard (e.g., cemented [cobalt] tungsten carbide) insert at the axial forward end thereof and is rotatably retained by a tool holder which is attached to a driven member such as, for example, a chain, a wheel, or a drum. Under the influence of the driven member, the hard insert of the cutting tool impinges the surface of the earth strata so as to break or fracture the earth strata. In addition to road planning, rotatable cutting tools have been used for coal mining, trenching, and drilling. U.S. Pat. No. B1 4,497,520 to Ojanen and U.S. Pat. No. 4,725,099 to Penkunas et al. disclose rotatable cutting tools for road planning applications.
Because of the severe operating environment, the hard insert, as well as the entire rotatable cutting tool, is subjected to great forces. These forces can destroy the hard insert if it does not possess adequate fracture toughness. Thus, it would be desirable if the design of the hard insert would enhance the fracture toughness thereof.
These forces can also destroy the cutting tool if it fails to effectively rotate in the tool holder. It would also be desirable to provide a hard insert of a design that enhances the rotation of the cutting tool during operation.
In one form thereof, the invention is a rotatable cutting tool for impinging the earth strata. The tool comprises an elongate tool body that has an axial forward end and a hard insert affixed to the tool body at the axial forward end thereof. The hard insert has a central longitudinal axis. The hard insert is rotatable about the central longitudinal axis.
The hard insert includes an axial forward tip section that has a generally conical shape and is of an axial length. The tip section has a starting included angle of between greater than about 110 degrees and less than about 140 degrees along the axial length of the tip section. A transition section is contiguous with and axially rearward of the tip section and at least a portion of the transition section presents a convex shape. The hard insert has a radially outwardly expanding first mediate section axially rearward of the transition section, and a base section axially rearward of the first mediate section.
In another form thereof, the invention is a rotatable cutting tool for impinging the earth strata. The tool comprises an elongate tool body that has an axial forward end, and a hard insert affixed to the tool body at the axial forward end thereof. The hard insert includes an axial forward tip section that has a generally conical shape and has a starting included angle of between greater that about 110 degrees and less than about 140 degrees. A transition section is contiguous with and axially rearward of the tip section and at least a portion of the transition section presents a convex shape. The hard insert has a radially outwardly expanding first mediate section axially rearward of the transitions section, and a base section axially rearward of the mediate section. The hard insert further includes a second mediate section axially rearward of and contiguous with the first mediate section, and the second mediate section having a generally frusto-conical shape.
In another form thereof, the invention is a hard insert for attachment to a rotatable cutting tool for impinging earth strata. The hard insert comprises an axial forward generally conical tip section presenting a tip surface and having a starting included angle of between greater that about 110 degrees and less that about 140 degrees, and a transition section continuous with and axially rearward of the tip section wherein at least a portion of the transition section presenting a convex shape. The hard insert further has a radially outwardly expanding first mediate section axially rearward of the transition section, and a base section axially rearward of the mediate section. The hard insert further includes a second mediate section having a cylindrical shape and being contiguous with the transition section and with the first mediate section.
In still another form thereof, the invention is a hard insert for attachment to a rotatable cutting tool for impinging earth strata. The hard insert comprises an axial forward generally conical tip section presenting a tip surface and having a starting included angle of between greater than about 110 degrees and less than about 140 degrees, and a transition section contiguous with and axially rearward of the tip section wherein at least a portion of the transition section presenting a convex shape. The hard insert has a radially outwardly expanding first mediate section axially rearward of the transition section, and a base section axially rearward of the mediate section, wherein the first mediate section has a generally frusto-conical shape and is contiguous with the transition section. The hard insert further has a second mediate section axially rearward of and contiguous with the first mediate section wherein the second mediate section has a generally frusto-conical shape, and the included angle of the first mediate section is less than the included angle of the second mediate section.
In still another form, the invention is an assembly for impinging earth strata under the influence of a driven member wherein the assembly comprises a tool holder and the tool holder contains a bore. The assembly further includes a rotatable cutting tool having an axial forward end and an axial rearward end. The cutting tool has a hard insert at the axial forward end thereof and a shank portion near the axial rearward end thereof wherein the shank portion carries a retainer. The hard insert has a central longitudinal axis and the hard insert being rotatable about the central longitudinal axis thereof. The cutting tool is held by the tool holder wherein the shank portion is within the bore of the tool holder. The hard insert includes an axial forward generally conical tip section that presents a tip surface. The tip section has an axial length. The tip section has a starting included angle of between greater than about 110 degrees and less than about 140 degrees along the axial length of the tip section. The hard insert has a transition section contiguous with and axially rearward of the tip section, and a radially outwardly expanding first mediate section axially rearward of the transition section, and a base section axially rearward of the first mediate section. The rotatable cutting tool has an operational orientation such that when the rotatable cutting tool is in a new condition a relief angle between the surface of the tip section and the surface of the earth strata is less than or equal to about zero degrees.
In yet another form thereof, the invention is a rotatable cutting tool for impinging the earth strata. The tool comprises an elongate tool body having an axial forward end, a hard insert affixed to the tool body at the axial forward end thereof. The hard insert has a central longitudinal axis and is rotatable about the central longitudinal axis. The hard insert includes an axial forward tip section having a generally conical shape and having an axial length. The tip section has a starting included angle of between greater than about 110 degrees and less than about 140 degrees along the axial length of the tip section. The hard insert has a chamfered section contiguous with and axially rearward of the tip section, a cylindrical mediate section being axially rearward of and contiguous with the chamfered section, a radially outwardly expanding mediate section axially rearward of the chamfered section, and a base section axially rearward of the radially outwardly expanding mediate section.
In still another form thereof, the invention is a hard insert for attachment to a rotatable cutting tool for impinging earth strata. The hard insert comprises an axial forward generally conical tip section presenting a tip surface and having a starting included angle of between greater than about 110 degrees and less than about 140 degrees, and a transition section contiguous with and axially rearward of the tip section wherein at least a portion of the transition section presenting a convex shape. Another portion of the transition section includes a chamfered section axially rearward of and contiguous with the convex section. The hard insert has a radially outwardly expanding first mediate section axially rearward of the transition section, and a base section axially rearward of the mediate section, wherein the first mediate section has a generally frusto-conical shape and is contiguous with the transition section. The hard insert further has a second mediate section axially rearward of and contiguous with the first mediate section wherein the second mediate section has a generally frusto-conical shape, and the included angle of the first mediate section is less than the included angle of the second mediate section.
In yet another form thereof, the invention is a rotatable cutting tool for impinging the earth strata. The tool comprises an elongate tool body having an axial forward end wherein the elongate body has a central longitudinal axis. The cutting tool is rotatable about the central longitudinal axis. A hard insert is affixed to the tool body at the axial forward end thereof. The hard insert has a central longitudinal axis that is coaxial with the central longitudinal axis of the tool body. The hard insert includes an axial forward tip section having a generally conical shape and having an axial length. At least a portion of tip section presents in cross-section a pair of oppositely disposed generally straight lines wherein the interior angle between the generally straight lines defines a starting included angle of the tip section. The starting included angle of the tip section is between greater than about 115 degrees and less than about 125 degrees along the axial length of the axial forward tip section. The hard insert has a radially outwardly expanding mediate section axially rearward of the tip section, and a base section axially rearward of the radially outwardly expanding mediate section.
In another form thereof, the invention is an assembly for impinging earth strata under the influence of a driven member wherein the assembly comprises a tool holder that contains a bore. The assembly includes a rotatable cutting tool having an axial forward end and an axial rearward end. The cutting tool has a hard insert at the axial forward end thereof and a shank portion near the axial rearward end thereof wherein the shank portion carries a retainer. The rotatable cutting tool has a central longitudinal axis. The cutting tool is rotatable about the central longitudinal axis. The hard insert has a central longitudinal axis that is coaxial with the central longitudinal axis of the tool body. The cutting tool is held by the tool holder wherein the shank portion is within the bore of the tool holder. The hard insert includes an axial forward generally conical tip section having an axial length. At least a portion of the tip section presents in cross-section a pair of oppositely disposed generally straight lines wherein the interior angle between the generally straight lines defines a starting included angle of the tip section. The starting included angle of the tip section is between greater than about 115 degrees and less than about 125 degrees along the axial length of the axial forward tip section. The hard insert has a radially outwardly expanding mediate section that is axially rearward of the tip section, and a base section that is axially rearward of the radially outwardly expanding mediate section. The rotatable cutting tool has an operational orientation such that a relief angle between the generally planar surface of the tip section and the surface of the earth strata is less than or equal to about zero degree.